Structural composites and other reinforced molded articles are commonly made by resin transfer molding and structural resin injection molding. These molding processes have been made more efficient by preforming the reinforcement fibers into a reinforcement layer or mat, which is the approximate size and shape of the molded article, prior to inserting the reinforcements into the mold. To be acceptable for production at an industrial level, a fast preforming process is required. In the manufacture of preforms, a common practice is to supply a continuous length of reinforcement strand or fiber to a chopper, which chops the continuous fiber into many discrete length fibers and deposits the discrete length fibers onto a collection surface. This process can be used to make preforms in an automated manner by mounting the reinforcement dispenser for movement over the collection surface and programming the movement of the dispenser to apply the reinforcement fibers in a predetermined, desired pattern. The reinforcement dispenser can be robotized or automated and such reinforcement fiber dispensers are known art for such uses as making preforms for large structural parts such as headliners, door panels and interior trim parts for the automotive industry.
Over the years the technical requirements for reinforcement products have increased and new methods have been developed for dispensing and laying down reinforcement fibers. Two of the more recently developed and effective methods are disclosed in U.S. Pat. Nos. 5,806,387 and 6,029,897 to Jander. In the Jander '387 patent a method for dispensing reinforcement fibers for the making of a preform or laminate includes winding a continuous length of a reinforcement fiber into coils around a form having a longitudinal axis. This is followed by the moving of the coils axially with respect to the form to engage a cutter. Next is the cutting of the coils to form discrete length reinforcement fibers. This is followed by the applying of a resinous material to the discrete fibers and the dispensing of the discrete length reinforcement fibers upon a molding surface.
In the Jander '897 patent the method for dispensing a reinforcement strand includes chopping the reinforcement strand into discrete reinforcement fibers and directing the reinforcement fibers into a dispensing nozzle so that the fibers travel along a path extending generally along a longitudinal axis of the nozzle. Next is the introducing of a fluid into the nozzle in a circumferential direction with respect to the longitudinal axis thereby creating a vortex of the fluid surrounding the fibers in the nozzle. This is followed by the dispensing of the reinforcement fibers onto a mold surface from the nozzle as a flow. That flow of fibers is controlled by controlling the fluid introduced into the nozzle.
While the devices disclosed in the Jander '387 and '897 patents have significantly improved the ability of the manufacturer to vary the delivery and particularly the width of the flow of chopped fibers dispensed by the fiber dispenser at the high speeds necessary for commercially successful operations, further advances in technology are still desired in order to increase the speed of the manufacturing process. The present invention meets this goal while also reducing production costs, eliminating the need for a mat made product and allowing greater input flexibility with respect to the use of a wide variety of natural and synthetic fiber materials.